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ing state of things lasted for a year. Five hundred paces from the island, the sea felt scalding hot to the hand, and melted away the pitch from boats, which had therefore to be prepared for the volcanic trip, by an extra caulking.

For 10 years after the formation of the new island, the volcano made several eruptions-but when examined in 1772 by M. de Choiseul, it was quite inactive; and a large quantity of bitumen and sulphur was observed oozing out of its shores.

Captain Tillard of the Royal Navy described in the Phil. Trans. for 1812, an analogous phenomenon which presented itself to his notice near the Azores. About a mile from the north-west cliffs of St. Michael's, within the sea, avolcano sprung up. From this part of the water an immense body of smoke was seen to rise, from which suddenly burst forth a black column of cinders, ashes, and stones, in the form of a spire inclined to the perpendicular at an angle of from ten to twenty degrees. During these eruptions, vivid flashes of lightning continually issued from the densest part of the volcanic smoke, accompanied with occasional water spouts. The part of the sea where the volcano was situated, was upwards of thirty fathoms deep. The volcano had lasted four days, when a crater began to form at the surface of the water, the edges of which rapidly rose to 20 feet above its level, with a diameter of about 400 feet The contiguous cliffs of St. Michael's were at this period shattered by a shock of an earthquake. The mouth of the crater facing St. Michael's was nearly level with the sea, though in other parts it eventually rose to a height of fully 200 feet. It

was filled with boiling hot water, which overflowed into the sea by a small channel of six yards broad; through which it was probably filled again at high water. This stream, close to the margin of the sea, was so hot, as to scald the fingers when they were suffered to remain in it a few seconds; and great numbers of fish were destroyed during the early part of the eruption. This island, called Sabrina, after the name of Captain Tillard's ship, was not long visible, for in 1812 nothing but a little smoke or steam was perceived to rise from the sea, where the volcanic ashes had been thrown up.

Appearances altogether similar occurred on May 10, 1814, during serene weather, on the coast of Kamtschatka.

In the history of volcanic eruptions, frequent mention is made of torrents of water and mud ejected by volcanoes. Bouguer and Condamine saw these formidable torrents tear up the surface of a whole country. Six hours after an explosion of Cotopaxi, a village nearly 80 miles distant in a straight line, and probably 140 by the winding channel, was entirely swept away by the flood. In 1698 the volcano of Carguarazo, contiguous to and probably connected with Chimboraço, sunk in, and covered nearly 50 square miles of country with mud. It is not in fact by burning lavas, that the volcanoes of Peru and Quito exercise their ravages, but by torrents of mud and water. The mud, when first ejected, has the consistence of pap, but it speedily hardens; and occasionally contains so much black combustible matter, that the inhabitants make use of it afterwards for fuel. Sometimes the muddy waters

MECHANISM OF THE GEYSER FOUNTAINS. 387

that flow from subterranean caverns, carry along with them a vast quantity of small fishes. These are a species of glutinous pimelodes (pimelodes cyclopum. Humb.), of which the largest are scarcely 4 inches long. Their number is often so considerable, that by putrifying they breed a pestilence in the country. They are of the same species as those living in the native streams; from which it would appear that there are certain communications between the upper level of the volcanic lakes in the interior of the mountains, and the surface of the external land. The wonderful circumstance is, that they are raised up from that level 8000 or 9000 feet high, and ejected from the crater with very little injury.

The masses of water and mud, in the preceding cases, are probably due to local peculiarities. There can however be no doubt that the expansion of water by heat into steam, forms the eruptive agent which elevates and throws out the liquid lavas of volcanoes, as well as the showers of ashes and stones. The fountains of the Geysers in Iceland, indisputably prove the volcanic agency of steam, so that Savery's engine is merely a miniature model of the mechanism employed by nature, on a magnificent scale, to give projectile force to her jets of hot water in Iceland. ،، For an hour and a half," says an intelligent traveller, "the column rose without interruption 150 feet high, being 17 feet thick at its greatest diameter; and spouted up with such energy, that it retained near the top, the same dimensions and the same figure as at the base. On throwing stones into the volcanic gulf, they were

seen to mount instantly with the column of water, and even to reach a still greater height with astonishing velocity."

Great volcanic eruptions are usually accompanied with very heavy rains, which inundate the contiguous regions. The sea seems to sympathise with the agitations of the adjoining volcanoes; rising and falling in rapid alternation. We may ascribe to a similar oscillation the depression which it suddenly undergoes in the neighbourhood of a volcano, at the crisis of an eruption, caused by the sudden deflux of a great body of water into the vast vol canic caverns. Earthquakes and volcanoes are intimately related. They are, says D'Aubuisson, most likely the effects of the same agents, or subterranean fires. In the tremendous earthquake which destroyed Lima in 1746, four volcanoes were opened up in one night, and the agitation of the ground immediately ceased. The deeper seated the explosive forces are, the more extensive and sudden is the concussion. At Cumana in 1812, the first shock lasted 6 seconds, the second 12; then a very loud subterranean noise was heard, followed by a perpendicular movement of 3 or 4 seconds'duration, which was terminated by a longer continued undulatory motion. Nothing on the surface of the ground could resist these cross oscillations. The city was totally overthrown, leaving only the cathedral. The ocean is very violently agitated by earthquakes. At that which desolated Lisbon in 1755, even the British and Norwegian seas felt the shock; and at the same instant the whole land of Portugal and Andalusia vibrated. In Africa when the

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cities of Morocco, Fez, and Mequinez were in a great degree destroyed, the sensation of the earthquake was perceived over a large portion of Spain, France, Switzerland, and Germany. The shock that ruined Lima, was propagated across the continent of America, and the Atlantic Ocean, even to Europe. A violent earthquake which not long ago overturned some houses at Constantinople, caused a concussion at Petersburgh. On the 8th Sept. 1601, between one and two o'clock in the morning, a considerable earthquake shook the whole of Europe and Asia.

Till Sir H. Davy's splendid discoveries of the metallic bases of the earths and alkalis in 1807 and 1808, no hypothesis explanatory of volcanoes had been offered which was entitled to the slightest respect. Ever since that most illustrious era, however, I have regarded the theory of volcanic action, equally complete and satisfactory, with most of our physical inductions. It is therefore peculiarly gratifying to find that its celebrated author has himself finally favoured the world with the development of views so entirely his own.

The metals of the alkalis and earths from their paramount affinity for oxygen, could not possibly exist on the surface, but only in the interior of the globe. On this principle, volcanic fires would be occasioned whenever these metals were extensively exposed to the action of air and water. Thus also, the formation of lavas might be explained, as well as that of granites, porphyries, basalts, and many other crystalline rocks, from the slow cooling of